You can tell if an area contains a magic portal. If you study an area for 1 round, you know the sizes and locations of any portals in the area. Once you find a portal, you can study it. (If you find more than one portal, you can only study one at a time.)

Each round you study a portal, you can discover one property of the portal, in this order: any key or command word needed to activate the portal, any special circumstances governing the portal's use (such as specific times when the portal can be activated), whether the portalis one-way or two-way, any of the usual properties listed in the "Building a Portal" section of the Forgotten Realms Campaign Setting (page 59), and finally, a glimpse of the area where the portal leads. You can look at the area where the portal leads for 1 round. Analyze portal does not allow other divination spells to extend through the portal. For example, you cannot also use detect magic or detect evil to study the area where the portal leads while viewing the area with analyze portal.

For each property, you make a caster level check (1d20 + caster level) against DC 17. If failed, you can try again the next round. Analyze portal has only limited ability to reveal unusual properties of portals, as follows:

Random Portals: The spell reveals only that the portal is random, and whether it can be activated now. It does not reveal when the portal starts and stops functioning.

Variable Portals: The spell reveals only that the portal is variable. If the caster studies the portal's destination, the spell reveals only the destination to which the portal is currently set.

Creature Only Portals: The spell reveals this property. If the caster studies the portal's destination, the spell reveals where the portal sends creatures. If it is the type of portal that sends creatures one place and their equipment another place, the spell does not reveal where the equipment goes.

Malfunctioning Portals: The spell reveals only that the portal is malfunctioning, not what sort of malfunction the portal produces.